Inflated reward value in early opiate withdrawal. (31st July 2014)

• Record Type: Journal Article
• Authors: Wassum, Kate M.; Greenfield, Venuz Y.; Linker, Kay E.; Maidment, Nigel T.; Ostlund, Sean B.
• Is Part Of: Addiction biology. Volume 21:Number 2(2016)
• Page Start: 221
• Page End: 233
• Publication Date: 2014-07-31
• Subjects: Chronic morphine -- incentive learning -- instrumental conditioning -- opiate withdrawal -- reward; Substance abuse -- Periodicals; Substance abuse -- Physiological aspects -- Periodicals; Substance-Related Disorders -- periodicals; 616.86
• DOI: 10.1111/adb.12172
• Languages: English
• ISSNs: 1355-6215

Abstract

Abstract: Through incentive learning, the emotional experience of a reward in a relevant need state (e.g. hunger for food) sets the incentive value that guides the performance of actions that earn that reward when the need state is encountered again. Opiate withdrawal has been proposed as a need state in which, through experience, opiate value can be increased, resulting in escalated opiate self‐administration. Endogenous opioid transmission plays anatomically dissociable roles in the positive emotional experience of reward consumption and incentive learning. We, therefore, sought to determine if chronic opiate exposure and withdrawal produces a disruption in the fundamental incentive learning process such that reward seeking, even for non‐opiate rewards, can become maladaptive, inconsistent with the emotional experience of reward consumption and irrespective of need. Rats trained to earn sucrose or water on a reward‐seeking chain were treated with morphine (10–30 mg/kg, s.c.) daily for 11 days prior to testing in withdrawal. Opiate‐withdrawn rats showed elevated reward‐seeking actions, but only after they experienced the reward in withdrawal, an effect that was strongest in early (1–3 days), as opposed to late (14–16 days), withdrawal. This was sufficient to overcome a negative reward value change induced by sucrose experience in satiety and, in certain circumstances, was inconsistent with the emotional experience of reward consumption. Lastly, we found that early opiate withdrawal‐induced inflation of reward value was blocked by inactivation of basolateral amygdala mu opioid receptors. These data suggest that in early opiate withdrawal, the incentive learning process is disrupted, resulting in maladaptive reward seeking. Abstract : This study evaluated the effect of opiate withdrawal on value‐driven reward seeking. In early withdrawal the experience‐dependent incentive value of both a sucrose and water reward was increased resulting in enhanced reward seeking. In certain circumstances, such reward seeking was inconsistent with the reward's emotional experience and occurred despite circumstances that would otherwise negatively impact reward value. Opiate withdrawal is, therefore, a distinct motivational state in which the general incentive learning process is altered resulting in maladaptive reward seeking.